Certain manufacturing processes require the attachment of overlapping ends of a precise length of material together to form a continuous loop of the material. Often, the precise length is cut from a continuous supply of the material. Heat treatment, or curing, is typically utilized to fuse the attached overlapping ends of the length of material together to increase the strength of the joint.
An example of such a manufacturing process is tire building, wherein a precise length of rubber or other material is wrapped around a mandrel or drum to form part of the tire. The length of rubber or other material is cut so that the ends of the length overlap to form a splice. The overlapping ends are temporarily attached together to form a loop of material which is then cured to strengthen the rubber.
The presence of a splice in the continuous loop of rubber or other material presents several problems. First, the double thickness of the spliced joint in the continuous loop of rubber or other material upsets the rotational balance of the tire formed therefrom. In addition, air is likely to be captured between the two overlapping ends of material, thereby weakening the resulting splice. Moreover, the entire material loop must be cured for the length of time required to cure the spliced joint of double thickness.
By reducing the length and the thickness of the splice, the rotational balance of the tire is improved. The area between the overlapping ends of rubber or other material is reduced, thereby minimizing the amount of air which can be captured therebetween to weaken the resulting joint. In addition, curing time for the continuous loop is reduced, permitting greater throughput by the associated curing equipment.
Devices for cutting sheets of material to be spliced together are known. For example, U.S. Pat. No. 4,426,901 to Hogan et al. discloses a cutter having heated, eccentrically mounted rollers which coact with each other to partially sever predetermined lengths of material from a continuous roll of the material. Retraction of a transport member, which works in conjunction with the eccentrically mounted rollers, completes the severing of the material. Material sheets having tapered ends are thereby provided using a two step process.
Thus, advantages exist for reducing the length and the thickness of spliced joints formed in materials used to manufacture tires. The present invention provides a simplified apparatus and method for affording these advantages, while providing a high degree of flexibility in design and operation.